Increased SHM per variable H-chain in Fas-deficient B cells. Somatic hypermutations per V region were calculated as the number of mutations in the CDR1-FR3 region per number of nucleotides present in the CDR1-FR3 in switched memory B cells of HD (data pooled from 3 donors), P1, and P2. ****P < .001 (2-way analysis of variance).